Photoaffinity Labeling of Luteinizing Hormone Releasing Hormone Receptor of Rat Pituitary Membrane Preparations

Specific LHRH receptor proteins of plasma membrane preparation from pituitary glands of the rat were identified using an 125I-labeled photoreactive LHRH derivative, [D-Lys6-N epsilon-azidobenzoyl]LHRH. This analog retained high binding affinity (apparent Kd value of 0.1 nM) to a single class of receptors. Sodium dodecyl sulfate polyacrylamide gel electrophoresis indicated the specific photolabeling of two proteins, a major band with an apparent molecular weight of 60,000 daltons and a minor band of 48,000 daltons. The latter is probably a degradation product of the receptor.